Gas metering pump



Dec. 31, 1957 I I c, M. GEORGE 2,818,208

GAS METERING P MP Filed April 28, 1955 FIG. I

' w/r/vsss J "1 1-i- MM CHARLES/l4. GEORGE BY x United States Patent GAS METERING PUMP Charles M. George, Maracaibo, Venezuela, assignor to the United States of America as represented by the United States Atomic Energy Commission The present invention relates to gas pumps and more particularly to liquid piston gas metering pumps.

The present invention is particularly useful in measur ing to very close tolerances the amountof gas pumped into a system. For example, in the process of hydrogenation it is often desirable to know exactly how much gas should be available to obtain the optimum reacting conditions.

It is the object of the present invention to provide a method and apparatus for'pumping a determinable quantity of gas in an accurate, simple and inexpensive manner.

It is another object of the present invention to provide a method and apparatus. for pumping a determinable quantity of gas in such a manner at relatively high pumping rates without requiring complicated valve mechanisms.

A further object of the present invention is to provide a method and apparatus for pumping determinable quantities of gas through the use of a liquid piston which controls the gas flow directly.

Other objects and advantages will become more apparent from the following description and drawings, hereby made a part of the specification, wherein:

Figure 1 shows a sectional View of one embodiment in accordance with the invention.

Referring to Figure 1, the preferred embodiment of the gas metering pump of the present invention comprises a base 1 having a control pressure passage 2, connected to any suitable controlled pressure source (not shown), and communicating with the area adjacent the upper surface of the base 1. A cylindrical flanged spacer 3 is attached and sealed to the upper surface of base 1, so that passage 2 communicates with the interior of spacer 3. Sealed to the upper flanges of spacer 3 is valve head 4. The valve head 4 has an inlet 5 which is connected to any suitable source of gas (not shown). The inlet 5 is connected through passage 6 to the chamber within spacer 3. The gas flows from inlet 5 into passage 6 through a bafile 7. Pumping chamber 8, having a predetermined volume, is also connected to the chamber within spacer 3, and is connected to passage 6 by means of a passage 9 located adjacent the bottom portion of valve head 4. Pumping chamber 8 contains a valve 10 at its outlet, which may be gravity or spring controlled depending upon the pressure of the gas to be metered. Fixed to the valve head 4 and extending downwardly into the chamber within spacer 3, is a cylindrical stop 11. Stop 11 is of thin-wall construction, has an outside diameter substantially equal to the inside diameter of spacer 3, and terminates a predetermined distance above the upper face of base 1.

Sealed to the lower portion of the valve head 4 and extending downwardly into the chamber of spacer 3 is bellows or similar compressible member 12 defining a compressible chamber, having its upper end open and its lower end closed. The inlet passage 6, pumping chamber 9, are all connected through the open end of bellows 12 to the interior thereof, so that the closed end of bellows 12 seals these passages from the control pressure passage 2.

' to force it open.

Fixed to the bottom of bellows 12 is stop plate 13, which isfreely movable within spacer 3 so that upon upward movement it will contact stop 11 and thereby be prohibited from any further upward motion.

The bellows 12 is filled with mercury or another similar liquid to a level proximate the bottom of valve head 4, when the bellows 12 is in its expanded position.

The operation of the device is as follows: A source of gas is connected to inlet 5. The gas flows through the bafile 7, passage 9' and will fill the chamber 8, its escape from chamber 8 being prevented by valve 10. Fluid pressure is applied through control pressure passage 2 which forces the stop plate 13 upwardly thereby compressing the bellows 12 and forcing the mercury or other liquid up the chamber 8 and passage 6. As the mercury level rises above the level indicated as 14, the gas source is no longer connected to chamber 8.' The provision of the small pas sage 9 is important because the accuracy of the metering is dependent thereon. Thus, it is apparent that, as the mercury moves upwardly toward the level 14, the gas within the chamber 8 will begin to work against the valve 10 However, the valve 10 is adjusted so that its opening inertia, either by virtue of gravity or a spring, is such that the level of the mercury must be above the level 14 before any opening action is effected. The mercury level continues to rise until the stop plate 13 comes into contact with the stop 11. At this point the mercury level is approximately at 15, i. e., below the level of the inlet 5. It should be noted that the inlet 5 determines the position. of. level 15. However, the inlet 5 may be placed in a higher position relative to level 15, if so desired, so that the level 15 is at the opening of valve 10. The gas which is sealed oflf in chamber 8 is compressed by the upward movement of the mercury and forces the valve 10 open thereby allowing the gas to escape into the connected system (not shown). The bafiie 7 inhibits the flow of mercury up the passage 6, so that no splashing of the mercury into inlet 5 takes place.

Upon releasing the control pressure in the control pressure passage 2, the resilient effect of bellows 12 will force the stop plate 13 downwardly, and the mercury will flow back into the interior of bellows 12. Additional resilient means may be provided, so that the control pressure fluid will be forced from interior of spacer 3 at faster rate. As the gas flows out through valve 10, the pressure is reduced within the chamber. When this pressure is no longer great enough to overcome the tendency of the valve 10 to move downwardly, the valve will close. Therefore, as the mercury level descends no back pumping takes place. As the mercury level moves below the passage 9, the chamber 8 will again be connected to the gas source through passage 6. Since a slight vacuum will be created in chamber 8 as the mercury level desdends, the gas in chamber 6 will flow into chamber 8 and the same gas pressure will be present in chamber 8 as is present in the inlet 5.

The advantage of using an expansible chamber such as a bellows in the present invention is two-fold. First, if the gas to be pumped is radioactive or toxic, there is no danger of this gas getting into the control pressure fluid thereby creating additional health hazards. Second, the type of fluid used in the control pressure system is not important, since it is merely used to compress the bellows. Also, the ratio of the volume of the pumping chamber to the volume of the liquid reservoir can be maintained constant, since the volume of the bellows at its compressed position is always the same. Thus, for a predetermined compression of the bellows, as controlled by stop 11, a constant amount of fluid will be displaced into the pumping chamber. In this manner the optimum pumping rate can be built into the device by selecting a given ratio between the volume of the fluid reservoir eas and the volume of the pumping chamber, so that relatively little movement of the bellows is required in order to move the liquid to the level 15. Since the ratio of these volumes is constant, then for a predetermined movement of the bellows the liquid level will move. to the same place. In this manner, the accuracy of the metering process does not change.

Because (a) the volume of pumping, chamber 8 is known, ([1) the distance between, levels 14 and, 15 can be easily determined, (c) the initial gas pressure is known, (d) the amount of pressure requiredj'to displace valve 10 can be determined, and (e) the; remaining volume of chamber 8 is, known, it can bev seen that the. amount of gas forced through the, valve 10, .canbe determined very accurately. I I v s Thus, it is apparentthat the presentinvention provides a novel method and, apparatus for pumping determinable quantities of gas, wherein the rate at which, the gas is P P 'm Y be ar ae a aw de an eens wherein the amount ofgas pumped. easily, determined,

While a certain specific embodiment has. been shown and described, it is understood that various modifications may be made without departing from the. scope of the invention as defined in the appended claims.

What is claimed is:

1. A gas metering pump c oniprising a resilient, cornpressible member defining a compressible chamber, said chamber having its top, end; open and containing a quantity of liquid at a first level; a valve, head located above and sealed to the. top ofsaid; compressible; member; said valve headforming an upwardly extending inlet passage connected tothe open, portion of said; compressible chamber, an upwardly extending pumping chamber connected to the open portion of said compressible chamber and a passage connecting the lower portion of said inlet passage and the lower portion of said pumping chamber; valve means in said valve head for controlling the flow of gas through said pumping chamber; and fluid means adjacent said compressible member for compressing said compressible member whereby the level of said liquid is moved above said connecting passage and into said pumping chamber to seal ofl? said pumping chamber from said inlet passage and to force the gas within said pumping chamber through said valve means;

2. A gas metering pump comprising a bellows having its top end. open and containing a quantity of liquid at a first level; a valve head sealed to the opened end of said bellows; said valve headforming an inlet passage, pumping chamber and connecting passage; said inlet passage extending upwardly from and communicating with the open end oil-said bellows; said; pumping chamber extending upwardly-from and communicating with the open end of said bellows and spaced. from. said inlet passage; said; pumping chamber and said inlet being connected by said passage proximate said first liquid level; valve-means in said valve head at the end opposite from said connecting passage for controlling: the flow. of gas. through said pumping chamber; and fluid means adjacent the bottom of said' bellows for compressing said bellows whereby the liquid is forced into said connecting passage sealing said pumping chamber-from said inlet passage and whereby the liquid forced into said pumping chamber compressing the gas therein.

No, references; cited 

